The placement of a bone graft between the vertebrae can be quite difficult. The graft is contoured to fit into the interbody space between the vertebrae. This space may have parallel sides, or have a slight dovetailed recess for graft reception. Either a parallel-sided or a dovetailed or keystone-shaped graft would be used, depending on the shape of the corresponding interbody space. Bone grafts may be placed between the vertebral bodies following removal of the intervertebral disk (interbody grafts) or following resection of all or part of one or more vertebral bodies (vertebral reconstruction). The technique of graft insertion is similar for these two processes, differing in the length or height of the graft which is to be inserted. Both techniques may be performed more easily using the Moskovich Facilitator.
Intervertebral disk prostheses are usually designed to be inserted into the interbody space after removal of the damaged intervertebral disk. The prostheses are usually designed to be fixed in place by an interference fit and frequently have metal endplates designed for bone ingrowth. Insertion of the prosthesis is correspondingly difficult due to the precision of fit required for successful operation of the device.
The prior art for interbody graft insertion makes a small pilot hole in the anterior part of the graft and a Cloward bone tamp is screwed into the graft. Up to 40 or 50 pounds distraction is then applied by the anesthesiologist to the head halter or to the skull tongs. After a few minutes of traction, which allows for stress relaxation, the graft is gently tamped into position. The instruments are then removed and the traction weights are released.
This prior art has numerous difficulties. The bone graft is usually small and easily damaged by drilling a hole into it, or by forcing it into a tight interbody space. Also, the graft can rotate during insertion or slip sideways, which may result in injury to delicate and important structures in the neck.
Another problem with the prior art is the application of a distraction force between the vertebrae, which the prior art requires from either longitudinal traction or the use of a spreader inserted between the vertebrae. Devices which screw into the vertebrae to provide distraction have been produced. This problem is even more difficult if a dovetail-shaped graft is used. If this type of graft is inserted with too little distraction, then the result may be the development of kyphosis (that is, forward bending posture) at the fusion site, or even graft dislodgement. Also, the use of a spreader to distract the interbody space is sometimes impossible because of limited space, or may cause fracture of a vertebra by the application of concentrated force by the inserted points of the spreader. Insertion of grafts at more than one level increases the level of difficulty encountered. Insertion of thoracic or lumbar or lumbosacral interbody grafts is made more difficult by the limited physical access to the vertebrae and the difficulty of obtaining distraction to insert the graft. In the presence of degenerative disease or chronic changes where the disk space has become narrow, the problem of adequate restoration of anatomic interbody height is exacerbated.
The Moskovich facilitator allows the surgeon to safely and accurately position the graft, even when it is necessary to apply force to the graft with a mallet, while also avoiding the problems of the prior art described above. The device can also be used to insert intervertebral disk prostheses. The device (of appropriate and proportional size) may be used at any level in the spine. SUMMARY OF THE INVENTION
The Moskovich facilitator facilitates the insertion of bone grafts between two vertebrae. The invention has two flat tong-like guides that distract the vertebrae as the graft slides between the two guides towards the vertebrae. The two guides have grooved surfaces to keep the graft from rotating or from slipping laterally. The two guides each have a lip to keep them from slipping too far in between the vertebrae. The two guides can be combined by an elbow piece into one part. The elbow is offset to permit impacting the graft directly on the angle of the axes of the guides. The two guides each have a notch, and the two notches hold an inserter/extractor. The screw-type inserter/extractor slowly rams the graft in between the vertebrae without impact, and slowly extracts the guides after the graft is seated.